Nonconjugated Polyene Copolymer, Rubber Composition and Uses Thereof

ABSTRACT

Disclosed are a conjugated polyene copolymer comprising a random copolymer having structural units derived from α-olefin (A1) of 2 to 20 carbon atoms and structural units derived from nonconjugated polyene (A2), said nonconjugated polyene copolymer having a glass transition temperature (Tg) of −25 to 20 □ and Mooney viscosity of [ML(1+4)100□] of 5 to 190; a rubber composition comprising the nonconjugated polyene copolymer and a diene-based rubber (B); a modifier for tires comprising the copolymer; a rubber material for tires comprising the rubber composition; a tire tread obtained from the rubber material for tires; and a tire having the tire tread.

TECHNICAL FIELD

The present invention relates to a nonconjugated polyene copolymer, arubber composition comprising the nonconjugated polyene copolymer and adiene-based rubber, and uses thereof.

BACKGROUND ART

There has heretofore been employed in general a diene-based rubbercomposition composed of a styrene/butadiene copolymer rubber (SBR) andnatural rubber for a rubber material for the tread tire of anautomobile. However, it has been desired for a tire to have, a highbraking performance in respect of the safety, in addition to abrasionresistance and lower fuel consumption concomitant with the recent trendof facilitation of energy economization.

[Patent Document 1] Japanese Unexamined Patent Application Publication(JP-A) No. 2001-114837

DISCLOSURE OF THE INVENTION

Therefore, the present inventors have proposed rubber materials for atire tread comprising as one component a nonconjugated cyclic polyenecopolymer having a specific content of nonconjugated cyclic polyene anda specific iodine value.

The present inventors have investigated and found that there is room forimprovement in terms of braking properties and fatigue resistance of atire and also in terms of mechanical strength of the tire.

An object of the present invention is to overcome the above problems andto provide a nonconjugated polyene copolymer which can be suitably usedas raw materials of a rubber material for tires, having both excellentbraking performance and fuel consumption performance, a rubbercomposition comprising the nonconjugated cyclic polyene copolymer, amodifier for tires comprising the nonconjugated polyene copolymer, arubber material for tires comprising the rubber composition, a tiretread produced from the rubber material for tires and a tire having thetire tread.

Another object of the present invention is to provide a nonconjugatedcyclic polyene copolymer which can be suitably used as raw materials ofa rubber material for tires, having improved braking performance andexcellent rubber elasticity, mechanical strength, weather resistance,ozone resistance and hardness, and further excellent fatigue resistance,in addition to excellent fuel consumption performance, a rubbercomposition comprising the nonconjugated cyclic polyene copolymer, amodifier for tires comprising the nonconjugated polyene copolymer, arubber material for tires comprising the rubber composition, a tiretread produced from the rubber material for tires and a tire having thetire tread.

A further object of the present invention is to provide a nonconjugatedcyclic polyene copolymer which can be suitably used as raw materials ofa rubber material for tires, having both excellent braking performanceand fuel consumption performance and further excellent mechanicalstrength, a rubber composition comprising the nonconjugated cyclicpolyene copolymer, a modifier for tires comprising the nonconjugatedpolyene copolymer, a rubber material for tires comprising the rubbercomposition, a tire tread produced from the rubber material for tiresand a tire having the tire tread.

A still further object of the present invention is to provide anonconjugated cyclic polyene copolymer which can be suitably used as rawmaterials of a rubber material for tires, having improved brakingperformance and excellent rubber elasticity, weather resistance, ozoneresistance and hardness, and further excellent mechanical strength, inaddition to excellent fuel consumption performance, a rubber compositioncomprising the nonconjugated polyene copolymer, a modifier for tirescomprising the nonconjugated polyene copolymer, a rubber material fortires comprising the rubber composition, a tire tread produced from therubber material for tires and a tire having the tire tread.

The present invention provides a nonconjugated polyene copolymercomprising a random copolymer having structural units derived fromα-olefin (A1) of 2 to 20 carbon atoms and structural units derived fromnonconjugated polyene (A2), the nonconjugated polyene copolymer has aglass transition temperature (Tg) of −25 to 20□ and Mooney viscosity of[ML(1+4)100□] of 5 to 190.

Further, the present invention provides a rubber composition comprisingthe nonconjugated polyene copolymer according to the invention and adiene-based rubber (B); a modifier for tires comprising the copolymeraccording to the invention; a rubber material for tires comprising therubber composition; a tire tread obtained from the rubber material fortires; and a tire having the tire tread.

The nonconjugated polyene copolymer according to the invention can besuitably used as raw materials of a rubber material for tires and can bealso used as a modifier for tires, having both excellent brakingperformance and fuel consumption performance. Further, since the rubbercomposition according to the invention comprises the nonconjugatedcyclic polyene copolymer, the composition can be used to obtain a tirehaving both excellent braking performance and fuel consumptionperformance. Furthermore, the rubber composition can be used as a rubbermaterial for tires. Since the tire tread according to the invention isproduced from the rubber material for tires, there can be provided atire having both excellent braking performance and fuel consumptionperformance. The tire according to the invention has both excellentbraking performance and fuel consumption performance, since the tire isprovided with the tire tread.

Further, the nonconjugated polyene copolymer according to the inventionis preferably any one of four copolymers given below. Hereinafter, thesecopolymers are referred to as a first nonconjugated polyene copolymer, asecond nonconjugated polyene copolymer and a third nonconjugated polyenecopolymer according to the invention, respectively.

The first nonconjugated polyene copolymer according to the invention isthe nonconjugated polyene copolymer according to the inventioncomprising a random copolymer having structural units derived fromα-olefin (A1) of 2 to 20 carbon atoms and structural units derived fromnonconjugated cyclic polyene (A3), wherein the content of structuralunits derived from α-olefin (A1) of 2 to 20 carbon atoms is more than 93to 96 mol % and the content of structural units derived fromnonconjugated cyclic polyene (A3) is 4 to less than 7 mol %.

The first nonconjugated polyene copolymer according to the invention isa specific nonconjugated cyclic polyene copolymer, and therefore can besuitably used as raw materials of a rubber material for tires, havingimproved braking performance and excellent rubber elasticity, mechanicalstrength, weather resistance, ozone resistance and hardness, and furtherexcellent fatigue resistance, in addition to excellent fuel consumptionperformance and can be also used as a modifier for tires. Theconventional copolymers have a large tan δ at 0° C., but they could notbe said to have sufficient braking performance. The first nonconjugatedpolyene copolymer according to the invention has, in particular, highbraking performance because it has an excellent balance between largetan δ at 0° C. and low hardness. The term “low hardness” means a largeground contact area and leads to having excellent braking performance.Further, a rubber composition using the first nonconjugated polyenecopolymer can obtain a tire having improved braking performance andexcellent rubber elasticity, mechanical strength, weather resistance,ozone resistance and hardness, and further excellent fatigue resistance,in addition to excellent fuel consumption performance, since it containsthe nonconjugated cyclic polyene copolymer.

The second nonconjugated polyene copolymer according to the invention isthe nonconjugated polyene copolymer according to the inventioncomprising a random copolymer having structural units derived fromα-olefin (A1) of 2 to 20 carbon atoms and structural units derived fromnonconjugated polyene (A2), wherein the content of structural unitsderived from α-olefin (A1) of 2 to 20 carbon atoms is 70 to 96 mol % andthe content of the structural units derived from nonconjugated polyene(A2) is 4 to 30 mol % and a decalin insoluble content at 135□ is 0.5% byweight or more.

The second nonconjugated polyene copolymer according to the invention isa specific nonconjugated polyene copolymer, and therefore can besuitably used as raw materials of a rubber material for tires, havingboth excellent braking performance and fuel consumption performance andfurther excellent mechanical strength and can be also used as a modifierfor tires. Further, a rubber composition using the second nonconjugatedpolyene copolymer can obtain a tire having both excellent brakingperformance and fuel consumption performance and further excellentmechanical strength, since it contains the nonconjugated cyclic polyenecopolymer.

The third nonconjugated polyene copolymer according to the invention isthe nonconjugated polyene copolymer according to the invention, being arandom copolymer from α-olefin (A1) of 2 to 20 carbon atoms andnonconjugated polyene (A2), which satisfies the following (iii) to (v)requirements:

(iii) an iodine value is 30 g/100 g or more;

(iv) it meets 0.0136≦(η_(0.1)*)^(0.3859)/η₁₀* wherein η_(0.1)* is aviscosity at 0.1 rad/sec (Pa·s) and η₁₀* is a viscosity at 10 rad/sec(Pa·s); and

(v) the content of the structural units derived from ethylene is in therange of 50 mol % or more based on 100 mol % of the total amount ofα-olefin (A1) having 2 to 20 carbon atoms and nonconjugated cyclicpolyene (A2) and a B value indicated below satisfies the relationship ofthe following formula [1]:B≦(1/a−1)×0.4+1  [1]wherein B=(c+d)/(2×a×(e+f)), in which a is an ethylene molar fraction; cis an ethylene/α-olefin dyad molar fraction; d is anethylene/nonconjugated polyene dyad molar fraction; e is an α-olefinmolar fraction; and f is a nonconjugated polyene molar fraction.

The third nonconjugated polyene copolymer according to the invention isa specific nonconjugated polyene copolymer, and therefore can besuitably used as raw materials of a rubber material for tires, havingimproved braking performance and excellent rubber elasticity, weatherresistance, ozone resistance and hardness, and further excellentmechanical strength, in addition to excellent fuel consumptionperformance, and can be also used as a modifier for tires. Further, arubber composition using the third nonconjugated polyene copolymer canobtain a tire having improved braking performance and excellent rubberelasticity, weather resistance, ozone resistance and hardness, andfurther excellent mechanical strength, in addition to excellent fuelconsumption performance, since it contains the nonconjugated cyclicpolyene copolymer.

PREFERRED EMBODIMENTS

Hereinafter, a nonconjugated polyene copolymer according to the presentinvention, a rubber copolymer and uses thereof will be specificallyexplained.

[Nonconjugated Polyene Copolymer]

The nonconjugated polyene copolymer according to the invention is arandom copolymer comprising structural units derived from α-olefin (A1)having 2 to 20 carbon atoms and structural units derived fromnonconjugated polyene (A2), in which it has a glass transitiontemperature (Tg) of −25 to 20° C. and a Mooney viscosity [ML(1+4)100°C.] of 5 to 190.

The glass transition temperature (Tg) of the nonconjugated polyenecopolymer according to the invention is −25 to 20° C., preferably −20 to10° C. When the nonconjugated polyene copolymer is used for a tire, itis possible to improve the gripping ability on the road face whilemaintaining rolling resistance during steady maneuvering as long as ithas the glass transition temperature (Tg) in this range. The glasstransition temperature (Tg) can be determined by a dynamicviscoelasticity measurements from the peak on the damping rate in themeasurement of the temperature dispersion.

The nonconjugated polyene copolymer according to the invention has aMooney viscosity [ML(1+4)100° C.] of 5 to 190, preferably 20 to 150,more preferably 30 to 110. When the nonconjugated polyene copolymer (A)has the Mooney viscosity in the above-mentioned range, the nonconjugatedpolyene copolymer (A) has excellent mechanical strength and workability,and when the nonconjugated polyene copolymer is used for a tire, thetire is excellent in braking performance.

In addition, the nonconjugated polyene copolymer according to theinvention is preferably any one of the following first to thirdnonconjugated polyene copolymers.

[First Nonconjugated Polyene Copolymer]

The first nonconjugated polyene copolymer is the nonconjugated polyenecopolymer according to the invention comprising a random copolymerhaving structural units derived from α-olefin (A1) of 2 to 20 carbonatoms and structural units derived from nonconjugated cyclic polyene(A3), wherein the content of structural units derived from α-olefin (A1)of 2 to 20 carbon atoms is more than 93 to 96 mol %, preferably 94 to 96mol %, and the content of structural units derived from nonconjugatedcyclic polyene (A3) is 4 to less than 7 mol %, preferably 4 to 6 mol %.

Since the first nonconjugated polyene copolymer has the content ofnonconjugated cyclic polyene (A3) in the above range, the firstnonconjugated polyene copolymer has lower hardness and provides tiresexhibiting higher braking performance-improving effects when it is usedin tires, as compared to a nonconjugated polyene copolymer having thecontent of nonconjugated cyclic polyene (A3) higher than the aboverange.

The iodine value of the first nonconjugated polyene copolymer is notparticularly limited, but preferably 55 g/100 g or less, more preferablyless than 50 g/100 g. In order to obtain a copolymer of the same Tg withsuch a low iodine value, as described in detail below, an effectivetechnique is to lower a B value.

[Second Nonconjugated Polyene Copolymer]

The second nonconjugated polyene copolymer is the nonconjugated polyenecopolymer according to the invention comprising a random copolymerhaving structural units derived from α-olefin (A1) of 2 to 20 carbonatoms and structural units derived from nonconjugated polyene (A2),wherein the content of structural units derived from α-olefin (A1) of 2to 20 carbon atoms is 70 to 96 mol %, preferably 80 to 96 mol %, morepreferably 88 to 96 mol %, and the content of the structural unitsderived from nonconjugated polyene (A2) is 4 to 30 mol %, preferably 4to 20 mol %, more preferably 4 to 12 mol %, and a decalin insolublecontent at 135□ is 0.5% by weight or more.

Since the second nonconjugated polyene copolymer has the content ofnonconjugated polyene (A2) in the above range, the second nonconjugatedpolyene copolymer has lower hardness and provides tires exhibitinghigher braking performance-improving effects when it is used in tires,as compared to a nonconjugated polyene copolymer having the content ofnonconjugated cyclic polyene (A2) higher than the above range.

A decalin insoluble content at 135° C. of the second nonconjugatedpolyene copolymer is 0.5% by weight or more, preferably 0.5 to 50% byweight, more preferably 0.5 to 30% by weight, and particularlypreferably 0.5 to 15% by weight. The decalin insoluble content at 135°C. in the above range is advantageous from the viewpoint of operationcontinuity in the case of a solution polymerization.

The measurement of the decalin insoluble content at 135° C. is carriedout as follows:

1. Measurement Method

(1) A sample is finely cut and 0.25 g (±10%) of the sample is weighed(A(g)).

(2) The weighed sample is introduced into a 500-ml Erlenmeyer flask and250 ml of decalin is added thereto.

(3) A rotator is placed in the Erlenmeyer flask and the flask is capped.

(4) The beaker is put in an aluminum block bath set at 140° C. (liquidtemperature: 135° C.) to preheat for 15 minutes.

(5) After 15 minutes, the rotator is rotated to carry out dissolutionunder stirring for 60 minutes.

(6) The weight of a 150-mesh stainless wire gauze vessel is weighed(B(g)).

(7) The dissolved sample is filtered using the wire gauze vessel.

(8) The inside of the flask is washed with fresh decalin (roomtemperature) and filtered (this operation is repeated three times).

(9) The inside of the wire gauze vessel is washed with fresh decalin(room temperature).

(10) The wire gauze vessel is dried for 1 hour using a vacuum drier at105±5° C.

(11) After standing to cool at room temperature for 1 hour, the weightof the wire gauze vessel is weighed (C(g)).

2. Calculation Method

Decalin Insoluble Content=(C−B)×100/A

Further, the iodine value is not particularly limited, but preferably 80g/100 g or less, more preferably less than 70 g/100 g.

[Third Nonconjugated Polyene Copolymer]

The third nonconjugated polyene copolymer is the nonconjugated polyenecopolymer according to the invention, being a random copolymer fromα-olefin (A1) of 2 to 20 carbon atoms and nonconjugated polyene (A2),which satisfies the following (iii) to (v) requirements:

(iii) an iodine value is 30 g/100 g or more;

(iv) it meets 0.0136≦(η_(0.1)*)^(0.3859)/η₁₀* wherein η_(0.1)* is aviscosity at 0.1 rad/sec (Pa·s) and η₁₀* is a viscosity at 10 rad/sec(Pa·s); and

(v) the content of the structural units derived from ethylene is in therange of 50 mol % or more based on 100 mol % of the total amount ofα-olefin (A1) having 2 to 20 carbon atoms and nonconjugated cyclicpolyene (A2) and the B value indicated below satisfies the relationshipof the following formula [1]:B≦(1/a−1)×0.4+1  [1]wherein B=(c+d)/(2×a×(e+f)), in which a is an ethylene molar fraction; cis an ethylene/α-olefin dyad molar fraction; d is anethylene/nonconjugated polyene dyad molar fraction; e is an α-olefinmolar fraction; and f is a nonconjugated polyene molar fraction.

The third nonconjugated polyene copolymer has the content of thestructural units derived from α-olefin (A1) of preferably 70 to 96 mol%, more preferably 80 to 96 mol %, particularly preferably 88 to 96 mol% and the content of the structural units derived from nonconjugatedpolyene (A2) of preferably 4 to 30 mol %, more preferably 4 to 20 mol %,particularly preferably 4 to 12 mol %. Since the third nonconjugatedpolyene copolymer has the content of nonconjugated polyene (A2) in theabove range, the third nonconjugated polyene copolymer has lowerhardness and provides tires exhibiting higher brakingperformance-improving effects when it is used in tires, as compared to anonconjugated polyene copolymer having the content of nonconjugatedpolyene (A2) higher than the above range.

The iodine value of the third nonconjugated polyene copolymer is 30g/100 g or more, preferably 30 to 100 g/100 g, more preferably 35 to 70g/100 g. The iodine value in the above range does not cause a problem instrength when it is used in tires.

The (η_(0.1)*)^(0.3859)/η₁₀* of the third nonconjugated polyenecopolymer satisfies 0.0136≦(η_(0.1)*)^(0.3859)/η₁₀*, preferably0.0141≦(η_(0.1)*)^(0.3859)/η₁₀*, more preferably0.0147≦(η_(0.1)*)^(0.3859)/η₁₀*. If the (η_(0.1)*)^(0.3859)/η₁₀*satisfies the above range, there is provided tires which has excellentstrength when it is used in tires. In order to adjust the(η_(0.1)*)^(0.3859)/η₁₀* to the above range, long chain branching may beintroduced onto a polymer by means of a method of copolymerizing amonomer having plural polymerizable double bonds, or a polymer having ahigh molecular weight may be added in a small amount.

These η_(0.1)* and η₁₀* values can be calculated from the followingmethod:

The frequency dependency of η* (complex viscosity coefficient) isdetermined, using a disk-shaped sample having a diameter of 25 mm and athickness of 2 mm, on a viscoelasticity tester (Model RDS II,manufactured by Rheometrics Inc.) under conditions of a measuringtemperature of 190° C., a frequency of 0.01 to 500 rad/s and a strainratio of 1.0%. η* at 0.1 rad/s is η_(0.1)* and η* at 10 rad/s is η₁₀*.This ratio is not large in general polymers. It is assumed that to havea relatively large ratio compared to general copolymers, is to have astructure containing much long chain branching.

[B Value]

In the nonconjugated polyene copolymer according to the invention, inorder to obtain the nonconjugated polyene copolymer having the same Tgwith a low content of nonconjugated cyclic polyene and/or a low iodinevalue, one technique is to produce a copolymer having a low B value.

From this viewpoint, the nonconjugated polyene copolymer according tothe invention is one preferred embodiment that the content of thestructural units derived from ethylene is in the range of 50 mol % ormore based on 100 mol % of the total amount of α-olefin (A1) having 2 to20 carbon atoms and nonconjugated cyclic polyene (A2) and further the Bvalue indicated below preferably satisfies the relationship of thefollowing formula [1], preferably the following formula [2], morepreferably the following formula [3], particularly preferably thefollowing formula [4]. Further, the above-mentioned third nonconjugatedpolyene copolymer has one condition satisfying the formula [1].B≦(1/a−1)×0.4+1  [1]B≦(1/a−1)×0.3+1  [2]B≦(1/a−1)×0.2+1  [3]B≦(1/a−1)×0.15+1  [4]

In order to produce the nonconjugated polyene copolymer in which the Bvalue satisfies the formula [1], for example, there is a method of usinga metallocene compound represented by the formula (8) or formula (9) tobe described below.

The B value is an index indicating randomness of the copolymerizedmonomer chain distribution.B≦(1/a−1)×0.4+1  [1]wherein B=(c+d)/(2×a×(e+f)), in which a is an ethylene molar fraction; cis an ethylene/α-olefin dyad molar fraction; d is anethylene/nonconjugated polyene dyad molar fraction; e is an α-olefinmolar fraction; and f is a nonconjugated polyene molar fraction.

Herein, the fractions a, c, d, e and f may be determined from a ¹³C-NMRspectrum on the basis of the report by J. C. Randall (Macromolecules,15, 353 (1982)) and J. Ray (Macromolecules, 10, 773 (1977)).

In this report, a dyad of carbon atoms (methylene group) in a polymermain chain is determined from a ¹³C-NMR spectrum of a copolymercomprising ethylene and propylene and the randomness and blockingproperties being the copolymerization form of the copolymer arediscussed by the sequence of the copolymer.

In the mathematical expression 1, both an α-olefin and nonconjugatedpolyene dyad molar fraction and a nonconjugated polyene andnonconjugated polyene dyad molar fraction are low, and thus are notconsidered in the invention. Further, an ethylene and nonconjugatedpolyene dyad molar fraction was twice of a nonconjugated polyene molarfraction.

In the formula [1], it shows that the larger the B value, the shorterthe block chain of α-olefin units or nonconjugated cyclic polyene unitsand the distribution of α-olefin units or nonconjugated cyclic polyeneunits is uniform. On the contrary, it shows that the smaller the Bvalue, the distribution of α-olefin units is not uniform and the longerthe block chain.

With respect to the nonconjugated polyene copolymer according to theinvention, the molar fraction is separately calculated from absorptionintensity based on a specific carbon of polyene and theethylene/nonconjugated polyene dyad molar fraction was calculated byrealizing the above assumption. The chain assignment by the othermethylene carbon was done according to the above literature.

Hereinafter, a method of calculating a B value is specifically shown asan application by taking as an example the nonconjugated cyclic polyenecopolymer obtained from ethylene, propylene and5-ethylidene-2-norbornene (ENB) being the copolymer according to theinvention.

First, the following nine NMR integration values of absorptionintensities for methylene carbons were obtained:(1)αβ,(2)αγ+αδ,(3)βγ,(4)βδ,(5)γδ,(6)δδ,(7)3E,(8)3Zand(9)αα+1Z+5E+5Z+6E+6Z

Herein, a symbol consisting of numbers and alphabetic characters in (7)to (9) is carbons derived from ENB, and the numbers indicate thepositions in the formula given below, and the alphabetic characters, Eand Z denote E isomer and Z isomer, respectively. Further, Greekcharacters indicate the positions of methylene carbon atoms locatedbetween carbon atoms on shortest main chain to which two methyl groupsare bonded, and a carbon atom adjacent to a carbon atom to which themethylene group is bonded is assumed as α. For example, the carbon atomon the main chain, which is adjacent to a carbon atom to which onemethyl group is bonded and is assigned to a carbon atom at the third indistance from the carbon atom to which the other methyl group is bonded,is αγ.

When the integration values were actually calculated, (2) was a total ofthe plural peaks near 37 to 39 ppm, (6) was a value obtained bysubtracting the γγ and γδ peaks from the total of the plural peaks near29 to 31 ppm, and (9) was the total of the plural peaks near 44 to 48ppm.

Further, αα was calculated as follows. The identification of the peakswas done according to the above literature:αα=αα+1Z+5E+6E+6Z−2×3E−3×3Z=(9)−2×(7)−3×(8)

Subsequently, the 6 dyads obtained from three monomers were calculatedfrom the obtained integration values as follows. Further, the dyads ofNN (ENB-ENB chain) and NP (ENB-propylene chain) derived from a smallcomposition of ENB was 0. The dyad of NE was twice the valuecorresponding to a molar fraction calculated from absorption intensityassigned to a carbon atom on a cyclic ENB.

PP (propylene-propylene chain)=αα+αβ/4

PE (propylene-ethylene chain)=αγ+αδ+αβ/2

EE (ethylene-ethylene chain)=(βδ+δδ)/2+(γδ+βγ)/4

NE (ENB-ethylene chain)=(3E+3Z)×2

Finally, each molar fraction of the composition was determined asfollows:

a (ethylene molar fraction)=(EE+PE/2)/(PP+PE+EE+3E+3Z)

c (ethylene/α-olefin dyad molar fraction)=PE/(PP+PE+EE+NE)

d (ethylene/nonconjugated polyene dyad molar fraction)=NE/(PP+PE+EE+NE)

e (cα-olefin molar fraction)=(PP+PE/2)/(PP+PE+EE+3E+3Z)

f (nonconjugated polyene molar fraction)=(3E+3Z)/(PP+PE+EE+3E+3Z)

Each molar fraction of the composition calculated above, is assigned tothe mathematical expression 1 to determine the mathematical expression2, and thus the B value was calculated:B=[(PE+NE)/(PP+PE+NE+EE)]/[(EE+PE/2)[(PP+PE/2)+(3E+3Z)]/(PP+PE+EE+3E+3Z)²]  [A]

In the mathematical expression A, it shows that the larger the B value,the shorter the block chain of α-olefin (propylene) units ornonconjugated cyclic polyene units and the distribution of α-olefin(propylene) units and nonconjugated cyclic polyene units is uniform. Onthe contrary, it shows that the smaller the B value, the distribution ofthe nonconjugated cyclic polyene copolymer is not uniform and the longerthe block chain.

The higher the block property, for example, when the cyclic polyene asthe comonomer is used in the same amount, Tg tends to increase. On thecontrary, the same Tg can be attained with a small amount of thecomonomer (cyclic polyene). Meanwhile, high Tg can be attained by theblock property and at the same time, the nonconjugated polyene copolymercan exhibit flexibility with much less amount of the comonomer (cyclicpropylene). As an index of flexibility, there may be exemplified an M100value in Examples described to be later.

[α-Olefin (A1)]

As the α-olefin (A1) constituting the nonconjugated polyene copolymeraccording to the invention, there may be exemplified those α-olefinhaving 2 to 20 carbon atoms, preferably 2 to 15 carbon atoms, such asethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodeceneand 4-methyl-1-pentene. These α-olefins (A1) may be used either alone orin a combination of two or more of them.

The nonconjugated polyene copolymer according to the invention maypreferably contain, as the structural units derived from α-olefin (A1),at least structural units derived from ethylene, in which the molarratio of the structural units derived from ethylene/structural unitsderived from α-olefin having 3 or more carbon atoms may be in the rangeof 100/0 to 1/99. Further, in the above-mentioned first and thirdnonconjugated polyene copolymers, the molar ratio of the structuralunits derived from ethylene/structural units derived from α-olefinhaving 3 or more carbon atoms may be in the range of more preferably100/0 to 50/50, particularly preferably 95/5 to 50/50. Furthermore, inthe above-mentioned second nonconjugated polyene copolymer, the molarratio of the structural units derived from ethylene/structural unitsderived from α-olefin having 3 or more carbon atoms may be in the rangeof more preferably 90/10 to 60/40.

[Nonconjugated Polyene (A2)]

As the nonconjugated polyene (A2) constituting the nonconjugated polyenecopolymer according to the invention, a compound having two or morenonconjugated unsaturated bonds can be used without any restriction andany of nonconjugated cyclic polyene (A3) and nonconjugated chain polyene(A4) can be used. In particular, at least part of the nonconjugatedpolyene (A2) is preferably the nonconjugated cyclic polyene (A3). Thecontent of the nonconjugated cyclic polyene (A3) is in the range ofpreferably 10 mol % or more, more preferably 30 mol % or more, and evenmore preferably 50 mol % or more based on 100 mol % of the total amountof the nonconjugated polyene (A2). Further, as a preferred embodiment,there may be exemplified one in which all the nonconjugated polyene (A2)is the nonconjugated cyclic polyene (A3).

Further, in the nonconjugated polyene copolymer according to theinvention, as the nonconjugated polyene (A2), there may be used any ofnonconjugated polyene (A2-1) having only one carbon-carbon double bondpolymerizable by a catalyst per molecule among carbon-carbon doublebonds present therein and nonconjugated polyene (A2-2) having twocarbon-carbon double bonds polymerizable by the catalyst per moleculeamong carbon-carbon double bonds present therein.

Among these, the nonconjugated polyene (A2-1) having only onecarbon-carbon double bond polymerizable, does not include a chainpolyene having vinyl groups (CH₂═CH—) at both ends thereof. If two ormore carbon-carbon double bonds are present in the nonconjugated polyene(A2-1), only one carbon-carbon double bond is present as a vinyl groupat the end of the molecule and the other carbon-carbon double bond (C═C)is preferably present by taking the internal olefin structure in themolecule chain (including main chain and side chain). Further, thenonconjugated cyclic polyene (A3) and the nonconjugated chain polyene(A4) include also the above-mentioned nonconjugated polyene (A2-1) andnonconjugated polyene (A2-2).

Specific examples of the nonconjugated cyclic polyene (A3) include acompound represented by the following formula (1-1):

wherein m is an integer of 0 to 2;

R¹ to R⁴ are each independently an atom or group selected from the groupconsisting of a hydrogen atom, a halogen atom and a hydrocarbon group.

Examples of the halogen atom represented by R¹ to R⁴ in the formula(1-1) include a fluorine atom, a chlorine atom, a bromine atom or aniodine atom.

Further, examples of the hydrocarbon group represented by R¹ to R⁴ inthe formula (1-1) include an alkyl group having 1 to 20 carbon atoms, ahalogenated alkyl group having 1 to 20 carbon atoms, a cycloalkyl grouphaving 3 to 15 carbon atoms, an aromatic hydrocarbon group having 6 to20 carbon atoms and an unsaturated hydrocarbon group having at least onedouble bond. More specifically, examples of the alkyl group include amethyl group, an ethyl group, a propyl group, an isopropyl group, anamyl group, a hexyl group, an octyl group, a decyl group, a dodecylgroup and an octadecyl group. Examples of the halogenated alkyl groupinclude those in which at least a part of the hydrogen atoms in theabove-mentioned alkyl group is substituted with a halogen atom such asfluorine, chlorine, bromine or iodine. Examples of the cycloalkyl groupinclude a cyclohexyl group. Examples of the aromatic hydrocarbon groupinclude a phenyl group and a naphthyl group. Examples of the unsaturatedhydrocarbon group include a vinyl group and an allyl group.

In the formula (1-1), any two of R¹ to R⁴, i.e., the pairs of R¹ and R²,R³ and R⁴, R¹ and R³, R² and R⁴, R¹ and R⁴, and R² and R³ each may bebonded to each other (under cooperation) to form a mono- or polycyclicring and the thus formed mono- or polycyclic ring may have doublebond(s).

Further, the pair of R¹ and R² or R³ and R⁴ in the formula (1-1) mayform together an alkylidene group. Such an alkylidene group is usuallyan alkylidene group having 1 to 20 carbon atoms and specific examplesthereof includes a methylene group (CH₂═), an ethylidene group (CH₃CH═),a propylidene group (CH₃CH₂CH═) and an isopropylidene group ((CH₃)₂C═).

Furthermore, the nonconjugated cyclic polyene (A3) represented by theformula (1-1) satisfies, for example, any of the following [i] to [iv]conditions: [i] R¹ to R⁴ are bonded to each other to form a mono- orpolycyclic ring having a double bond; [ii] an alkylidene group is formedfrom the pair of R¹ and R² or R³ and R⁴; [iii] R¹ and R³ or R² and R⁴are bonded to each other to form a double bond; and [iv] at least one ofR¹ to R⁴ represents an unsaturated hydrocarbon group having one or moredouble bonds.

Specific examples of the nonconjugated cyclic polyene (A3) representedby the formula (1-1) include alkylidene group-containing nonconjugatedcyclic polyenes (A3-1) which has an alkylidene group formed from thepair of R¹ and R² or R³ and R⁴, polycyclic nonconjugated cyclic polyenes(A3-2) in which any two of R¹ to R⁴ may be bonded to each other to forma mono- or poly-cyclic ring having one or more double bond, unsaturatedhydrocarbon group-containing nonconjugated cyclic polyenes (A3-3) inwhich at least one of R¹ to R⁴ is a monovalent unsaturated hydrocarbongroup having one or more double bonds and ring-symmetrical nonconjugatedcyclic polyenes (A3-4) in which either R¹ and R³ or R² and R⁴ are bondedto form a double bond so that the resulting cyclic polyene has abilaterally symmetry with respect to a line connecting the bridgeheadcarbon atoms or the commonly shared carbon atoms of the condensed ringwith each other as an axis of symmetry.

Specific examples of the alkylidene group-containing nonconjugatedcyclic polyenes (A3-1) include those which are represented by thefollowing formula (1-2):

wherein s represents an integer of 0 to 2; R¹⁷ represents an alkylidenegroup; R¹⁸ and R¹⁹ each independently represents an atom or a groupselected from the group consisting of a hydrogen atom, a halogen atomand a hydrocarbon group and R¹⁸ and R¹⁹ may form together an alkylidenegroup.

Specific examples of the alkylidene group represented by R¹⁷ in theformula (1-2), include those having 1 to 20 carbon atoms, such as amethylene group, an ethylidene group, a propylidene group and anisopropylidene group.

The symbol s in the formula (1-2) preferably represents 0. Examples ofthe halogen atom represented by R¹⁸ and R¹⁹ include the same as thosedescribed above. Examples of the hydrocarbon group include an alkylgroup having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to20 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms and anaromatic hydrocarbon group having 6 to 20 carbon atoms.

Specific examples of the alkylidene-containing nonconjugated cyclicpolyene (A3-1) represented by the formula (1-2) include5-methylene-2-norbornene, 5-ethylidene-2-norbornene (ENB),5-isopropylidene-2-norbornene and the compounds given below. Among them,5-ethylidene-2-norbornene is preferred.

Specific examples of the above-mentioned polycyclic nonconjugated cyclicpolyene (A3-2) include dicyclopentadiene (DCPD),dimethyldicyclopentadiene and the compounds given below.

Specific examples of the above-mentioned unsaturated hydrocarbongroup-containing nonconjugated cyclic polyene (A3-3) include5-vinyl-2-norbornene and the compounds given below.

Specific examples of the above-mentioned ring-symmetrical nonconjugatedcyclic polyene (A3-4) include the compounds given below.

For the nonconjugated cyclic polyene (A3) represented by the formula(1-1), those in which m represents 0 are preferred, and in particular,the alkylidene group-containing nonconjugated cyclic polyenes (A3-1) inwhich m in the formula (1-1) represents 0, namely, the alkylidenegroup-containing nonconjugated cyclic polyenes (A3-1) in which s in theformula (1-2) represents 0, or the polycyclic nonconjugated cyclicpolyenes (A3-2) in which m in the formula (1-1) represents 0, areparticularly preferred. Most preferred ones among them are thealkylidene group-containing nonconjugated cyclic polyenes (A3-1) inwhich s in the formula (1-2) represents 0, and specifically5-ethylidene-2-norbornene (ENB) is most preferable.

Specific representative examples of the nonconjugated chain polyene (A4)include 1,4-hexadiene, 1,5-heptadiene and 1,6-octadiene, which arestraight-chain, and 7-methyl-1,6-octadiene and6,7-dimethyl-1,6-octadiene, which have a branch-chain.

Examples of the other nonconjugated chain polyenes include α,ω-dienesuch as 1,7-octadiene and 1,9-decadiene.

Further, examples of the other nonconjugated chain polyenes (A4) includenonconjugated trienes or tetraenes (A4-1) represented by the followingformula (2-1):

wherein p and q are 0 or 1 with the proviso that p and q are notsimultaneously 0;

f is an integer of 0 to 5 with the proviso that f is not 0 when both pand q are 1;

g is an integer of 1 to 6;

R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are each independently a hydrogen atom oran alkyl group having 1 to 3 carbon atoms;

R⁸ is an alkyl group having 1 to 3 carbon atoms; and

R⁹ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or agroup represented by —(CH₂)_(n)—CR¹⁰═C(R¹¹)R¹² wherein n is an integerof 1 to 5, R¹⁰ and R¹¹ are each independently a hydrogen atom or analkyl group having 1 to 3 carbon atoms and R¹² is an alkyl group having1 to 3 carbon atoms, with the proviso that R⁹ is a hydrogen atom or analkyl group having 1 to 3 carbon atoms when both p and q are 1.

Among nonconjugated trienes or tetraenes (A4-1) represented by theformula (2-1), nonconjugated trienes (A4-2) represented by the followingformula (2-2) are preferable in view of the balance between the brakingperformance and the fuel consumption performance, vulcanization feature,processing performance on the vulcanization (scorching stability) andthe like.

wherein R¹ to R⁵ are each independently a hydrogen atom, a methyl groupor an ethyl group, with the proviso that R⁴ and R⁵ do not simultaneouslyrepresent a hydrogen atom.

Further, the nonconjugated trienes (A4-2) represented by the formula(2-2) correspond to the nonconjugated trienes or tetraenes (A4-1)represented by the formula (2-1), above all, the nonconjugated trieneswherein f is 0, g is 2, p is 0, q is 1 and R⁵ and R⁶ are a hydrogenatom. Among the nonconjugated trienes (A4-2) represented by the formula(2-2), the compounds in which both R³ and R⁵ are a methyl group arepreferred. The nonconjugated polyene copolymer according to theinvention obtained using such nonconjugated triene (A4-2) as monomer rawmaterials can be used for the rubber composition to be described laterand from which tires superior especially both in the braking performanceand the fuel consumption performance can be produced.

Specific examples of the nonconjugated trienes or tetraenes (A4-1)represented by the formula (2-1) include compounds given below(excluding those falling under the formula (2-2)):

Specific examples of the nonconjugated trienes (A4-2) represented by theformula (2-2) include compounds given below:

The nonconjugated trienes or tetraenes (A4-1) represented by the formula(2-1) can be produced by a known method, for example, methods in detaildescribed in JP-A No. 9-235327 and 2001-114837 filed by the presentapplicant.

[Process for Producing Nonconjugated Polyene Copolymer]

The nonconjugated polyene copolymer according to the present inventioncan be produced by copolymerizing an α-olefin (A1) and a nonconjugatedpolyene (A2), preferably the α-olefin (A1) and a nonconjugated cyclicpolyene (A3), in the presence of a catalyst.

As the catalyst used in the production of the first nonconjugatedpolyene copolymer, for example, those which are composed of a transitionmetal compound (C), such as a compound of vanadium (V), zirconium (Zr)and titanium (Ti), and an organoaluminum compound or anorganoaluminum-oxy compound (D) and/or an ionizing ionic compound (E)may be employed. Examples of the catalyst used in the production of thesecond nonconjugated polyene copolymer include a vanadium-based catalystcomposed of a soluble vanadium compound (c-1) and an organoaluminumcompound (d-1). As the catalyst used in the production of the thirdnonconjugated polyene copolymer, for example, those which are composedof a transition metal compound (C), such as a compound of zirconium (Zr)and titanium (Ti), and an organoaluminum compound or anorganoaluminum-oxy compound (D) and/or an ionizing ionic compound (E)may be employed.

Specific examples of the catalyst include (1) a vanadium-based catalystcomposed of a soluble vanadium compound (c-1) and an organoaluminumcompound (d-1), and (2) a metallocene-based catalyst composed of ametallocene compound (c-2) of a transition metal selected from metals ofGroup 4 elements of the periodic table of elements of 1 to 18 groups(which applies to all the cases in the following), an organoaluminum-oxycompound (d-2) and/or an ionizing ionic compound (e-1).

Examples of the soluble vanadium compound (c-1) constituting thevanadium-based catalyst include vanadium compounds represented by theformulae (3) or (4) given below:VO(OR)_(a)X_(b)  (3)VO(OR)_(c)X_(d)  (4)wherein R represents a hydrocarbon group; X represents a halogen atom;and a, b, c and d each satisfies 0≦a≦3, 0≦b≦3, 2≦a+b≦3, 0≦c≦4, 0≦d≦4 and3≦c+d≦4.

As the soluble vanadium compound (c-1), electron donor-added products ofsoluble vanadium compounds obtained by contacting with an electron donormay also be employed.

As the organoaluminum compound (d-1) for forming the vanadium-basedcatalyst, those in which at least one Al—C bond is included in themolecule can be employed. Examples of such a compound includeorganoaluminum compounds represented by the following formula (5):(R¹)_(m)Al(OR²)_(n)H_(p)X_(q)  (5)wherein R¹ and R² represent each a hydrocarbon group which may beidentical with or different from each other and which has usually 1 to15 carbon atoms, preferably 1 to 4 carbon atoms; X represents a halogenatom; and m, n, p and q each represent a numeral which meets 0<m≦3,0≦n<3, 0≦p<3 and 0≦q<3, with m+n+p+q=3.

The metallocene compound (c-2) constituting the metallocene-basedcatalyst is that of a metal selected from the transition metals of Group4 of the periodic table and is, specifically, one represented by thefollowing formula (6):MLx  (6)wherein M represents a transition metal selected from the Group 4 of theperiodic table; x represents the valence of the transition metal M; andL represents a ligand.

Specific examples of the transition metal in the formula (6) representedby the symbol M include zirconium, titanium and hafnium. The ligands Lin the formula (6) coordinate to the transition metal M, wherein atleast one of these ligands L has a cyclopentadienyl skeleton.

In the case where the compound represented by the formula (6) has two ormore groups having a cyclopentadienyl skeleton as a ligand L, two ofthese groups having a cyclopentadienyl skeleton may be bonded togetherthrough an alkylene group which may have a substituent or through asubstituted silylene group.

When the transition metal of the metallocene compound represented by theformula (6) has a valence of 4, it is represented more specifically bythe formula (7):R_(k) ²R_(l) ³R_(m) ⁴R_(n) ⁵M  (7)wherein M is the same transition metal as that given in the formula (6),R² represents a group (ligand) having a cyclopentadienyl skeleton; R³,R⁴ and R⁵ each independently represent a group (ligand) with or withouta cyclopentadienyl skeleton; and k is an integer of 1 or greater,wherein k+1+m+n=4.

As the metallocene compound (c-2), there may also be employed those ofbridged structure in which, in the above formula (7), at least two ofthe ligands R², R³, R⁴, and R⁵, for example, R² and R³ are the group(ligand) having a cyclopentadienyl skeleton and such at least two groupsare bonded to each other through an alkylene group, a substitutedalkylene group, a silylene group or a substituted silylene group.

It is also possible to use compounds represented by the formula (8)given below, as the metallocene compound (c-2).LaMX₂  (8)in which M is a metal of Group 4 or of the lanthanide series of theperiodic table; La represents a derivative of nonlocalized π-bondinggroup which provides the active site of the metal M with a captivegeometry, and the two X's each independently represent a hydrogen atom,a halogen atom, a hydrocarbon group having 20 or less carbon atoms, asilyl group having 20 or less silicon atoms or a germyl group having 20or less germanium atoms.

Among these compounds represented by the formula (8), preferred arethose represented by the following formula (9):

wherein M is titanium, zirconium or hafnium; X has the same meaning asthat of the formula (8); Cp represents a substituted cyclopentadienylgroup having a substituent Z and bonded to M by π-bonding; Z representsan oxygen atom, a sulfur atom, a boron atom or an element of Group 14 ofthe periodic table, such as silicon, germanium or tin; and Y is a ligandcontaining nitrogen, phosphorus, oxygen or sulfur, wherein Z and Y mayform together a condensed ring.

As the metallocenes compound (c-2) represented by the formula (8) or(9), a titanium compound in which the central metal atom is titanium andwhich have a ligand containing one cyclopentadienyl skeleton maypreferably be used. As one method for the nonconjugated polyenecopolymer according to the invention in which the B value satisfies theformula [1], there is a method of using the metallocene compoundrepresented by the formula (8) or formula (9).

Next, the description is directed to the organoaluminum oxy-compound(d-2) and to the ionizing ionic compound (e-1) to be used for preparingthe metallocene catalyst. As the organoaluminum-oxy compound (d-2),known aluminoxanes or benzene-insoluble organoaluminum-oxy compounds(d-2) may be used.

Specifically, these known aluminoxanes are represented by the followingformula (11) or (12):

wherein R is a hydrocarbon group, such as a methyl group, an ethylgroup, a propyl group and a butyl group, preferably a methyl group andan ethyl group, particularly preferably a methyl group; and m is aninteger of 2 or greater, preferably of 5 to 40.

As the ionizing ionic compound (e-1), which may sometimes be referred toas an ionic ionizing compound or ionic compound, there may beexemplified Lewis acids, ionic compounds, borane compounds and carboranecompounds.

For producing the nonconjugated polyene copolymer according to theinvention, the α-olefin (A1) and the nonconjugated polyene (A2) aresubjected to copolymerization usually in a liquid phase in the presenceof the desired catalyst. Here, a hydrocarbon solvent is generally used,but monomers may be used as the solvent.

The copolymerization may be carried out in a batchwise or continuousway. On carrying out the copolymerization in batchwise way, the catalystis used at the desired concentration.

Temperature and pressure in the copolymerization may be suitablyselected depending on types of a monomer and a catalyst. In general, thecopolymerization may be carried out under optimal conditions in whichthe temperature is in the range of −50 to 150° C. and the pressure is inthe range of 0 to 7.8 MPa.

In particular, when the second nonconjugated polyene copolymer accordingto the invention is produced, it is preferable to employ a method inwhich the nonconjugated polyene (A2-1) and the nonconjugated polyene(A2-2) are used together in the presence of the vanadium-based catalystunder the above-mentioned conditions to polymerize, or a method in whichthe nonconjugated polyene (A2-2) is used to polymerize at a high polymerconcentration or much higher polymer concentration and/or an iodinevalue is increased to increase the insoluble content.

Further, in particular, when the third nonconjugated polyene copolymeraccording to the invention is produced, it is preferable to employ amethod in which the nonconjugated polyene (A2-1) and the nonconjugatedpolyene (A2-2) are used together, similarly in the presence of themetallocene catalyst which is preferably used in the production of thefirst nonconjugated polyene copolymer according to the invention, underthe above-mentioned conditions to polymerize, or a method in which thenonconjugated polyene (A2-2) is used to polymerize at a relatively highpolymerization temperature of 90° C. or more, preferably 110° C. ormore.

In the production of the second and third nonconjugated polyenecopolymers according to the invention in which the nonconjugated polyene(A2-1) and the nonconjugated polyene (A2-2) are preferably used, it ispreferable to set such that the content of the structural units derivedfrom nonconjugated polyene (A2-1) is 1/10 to 1000-fold moles, preferably1/10 to 500-fold moles of the structural units derived fromnonconjugated polyene (A2-2).

On the copolymerization, the α-olefin (A1) and the nonconjugated polyene(A2) are supplied to the polymerization system in such an amount thatthe nonconjugated polyene copolymer is obtained in the compositionspecified above. Further, on the copolymerization, a molecular weightregulator such as hydrogen may be also used.

By performing the copolymerization as described above, the nonconjugatedpolyene copolymer according to the invention is usually obtained as apolymerization solution containing it. This polymerization solution istreated in a usual way to obtain the nonconjugated polyene copolymer.

[Rubber Composition]

The rubber composition according to the present invention is a rubbercomposition comprising the nonconjugated polyene copolymer according tothe invention (hereinafter denoted as the nonconjugated polyenecopolymer (A)) and a diene-based rubber (B), wherein the proportion ofthe contents of these components, the nonconjugated polyene copolymer(A)/diene rubber (B) in a weight ratio, is in the range of 60/40 to0.1/99.9, preferably 50/50 to 1/99, more preferably 40/60 to 5/95. Whenthe proportion of the contents of both components is in the range givenabove, it is possible to produce tires which have both excellent brakingperformance and fuel consumption performance, and to obtain the rubbercomposition which can reveal excellent features in the improved weatherresistance, in the controlled damping rate and the like, wherein thecloser the weight ratio to the above-mentioned preferable range or themore preferable range is, the more excellent the rubber composition inthe balance between the braking performance and the fuel consumptionperformance and in the improved weather resistance, in the controlleddamping rate will be.

Since the nonconjugated polyene copolymer (A) is used in the inventionand thus particularly the hardness after covulcanization with thediene-based rubber (B) can be decreased, it is preferably used for thetires.

As the diene-based rubber (B) used in the invention, every knowndiene-based rubber having double bond(s) in the main chain and having atleast partially structural units derived from a conjugated dienecompound can be used without limitation, but a polymer or copolymerrubber made from the conjugated diene compound as the main monomer ispreferred. The diene-based rubber (B) includes natural rubber (NR) andhydrogenated rubber. For the diene-based rubber, those which have iodinevalues of 100 or more, preferably 200 or more, more preferably 250 ormore are preferred.

Specific examples of the diene-based rubber (B) include natural rubber(NR), isoprene rubber (IR), styrene/butadiene rubber (SBR), butadienerubber (BR), chloroprene rubber (CR), acrylonitrile/butadiene rubber(NBR), nitrile rubber and hydrogenated nitrile rubber. Among them,natural rubber (NR), isoprene rubber (IR), styrene/butadiene rubber(SBR) and butadiene rubber (BR) are preferred, particularly preferablystyrene/butadiene rubber (SBR). The diene-based rubbers (B) may be usedeither solely or in a combination of two or more of them.

As the natural rubber (NR), those standardized by Green Book(international package standards for qualities of commercial grades ofnatural rubber) may be used. As the isoprene rubber (IR), those havingspecific gravities in the range of 0.91 to 0.94 and Mooney viscosity[ML(1+4)100° C.] in the range of 30 to 120 may be preferably used.

As the styrene/butadiene rubber (SBR), those having specific gravitiesin the range of 0.91 to 0.98 and Mooney viscosity [ML(1+4)100° C.] inthe range of 20 to 120 may be preferably used. As the butadiene rubber(BR), those having specific gravities in the range of 0.90 to 0.95 andMooney viscosity [ML(1+4)100° C.] in the range of 20 to 120 may bepreferably used.

The rubber composition according to the invention is a rubbercomposition capable of being vulcanized. While it may be used as anunvulcanized product, more excellent features may be revealed by usingit as a vulcanized product. The vulcanization may be carried out by amethod of heating with a vulcanizing agent (F) or by a method ofirradiation of electron beam without using the vulcanizing agent (F).

When the rubber composition is vulcanized by heating it, compoundsconstituting a vulcanizing system comprising a vulcanizing agent (F), avulcanization accelerator, a vulcanization aid and the like may beadmixed to the rubber composition. As the vulcanizing agent (F), forexample, conventionally known various vulcanizing agents such as sulfur,sulfur compounds, organic peroxides and the like may be used. Among theabove various vulcanizing agents, sulfur and sulfur compounds arepreferred, particularly preferably sulfur, since a rubber compositionhaving excellent characteristic properties can be obtained by the usethereof. In the case that the vulcanizing agent is sulfur or sulfurcompounds, it may be added in an amount of 0.1 to 10 parts by weight,preferably 0.5 to 5 parts by weight, based on 100 parts by weight of thetotal amount of the nonconjugated polyene copolymer (A) and thediene-based rubber (B). In the case the vulcanizing agent is organicperoxides, it may be added in an amount of 0.05 to 15 parts by weight,preferably 0.15 to 5 parts by weight, based on 100 parts by weight ofthe total amount of the nonconjugated polyene copolymer (A) and thediene-based rubber (B). When sulfur or a sulfur compound is used as thevulcanizing agent, it is preferable to use in combination with avulcanization accelerator. When the organic peroxide is used as thevulcanizing agent, it is preferable to use in combination with avulcanization aid.

The rubber composition according to the present invention may contain afiller (G) comprising a reinforcing agent such as carbon black andinorganic fillers; and a softener such as petroleum-based, coaltar-based, fatty oil-based softeners, waxes, fatty acid salts, andsynthetic polymeric substances. The rubber composition according to thepresent invention may contain, as various agents, for example, acompound constituting a foaming agent system such as a foaming agent anda foaming aid, an antioxidant (stabilizer), a processing aid, aplasticizer, a colorant and other rubber compounding agents. The typesand formulating amounts of these agents may be suitably selecteddepending on uses.

[Preparation of Rubber Composition]

The rubber composition according to the present invention may beprepared from the nonconjugated polyene copolymer (A) and thediene-based rubber (B) together with the optionally incorporated othercomponents given above by a preparation technique used in general forpreparing rubber blends. It may be prepared by, for example, kneadingthe nonconjugated polyene copolymer (A), the diene-based rubber (B) andthe optionally incorporated other components on an internal mixer suchas a Banbury mixer, a kneader or Intermix, at a temperature of 80 to170° C. for 3 to 10 minutes; admixing thereto a vulcanizing agent (F)and, if necessary, a vulcanization accelerator, a vulcanization aid, afoaming agent and the like to knead the resulting mixture on a roll oron a kneader at a roll temperature of 40 to 80° C. for 5 to 30 minutes;and taking out the kneaded mass in portions. In this manner, the rubbercomposition (rubber blend) is prepared usually in a form of ribbon orsheet. In the case where a low kneading temperature is permitted in theinternal mixer, the vulcanizing agent (F), a vulcanization accelerator,a foaming agent and the like may be simultaneously admixed thereto.

The vulcanized product (vulcanized rubber) of the rubber compositionaccording to the invention may be usually obtained by subjecting theunvulcanized rubber composition described above to a preliminary formingby various forming techniques using forming apparatuses such as anextrusion molding machine, a calendar roll, a press machine, aninjection molding machine and a transfer molding machine, into a desiredform and effecting the vulcanization of the resulting formed product,simultaneously with this forming or after the formed product has beentransferred to a vulcanization vessel, by heating it or irradiating itby an electron beam. In the case of the foamed product, the unvulcanizedrubber blend containing a foaming agent is subjected to vulcanization,as described above, wherein foaming of the formed product issimultaneously attained with the vulcanization so as to obtain a foamedproduct.

In the case of vulcanizing the rubber composition by heating, it ispreferable to employ a heating vessel embodiment such as in a heatingmode by hot air, glass beads fluidized bed, ultrahigh frequencyelectromagnetic wave (UHF), steam or hot molten-salt bath (LCM), at atemperature of 150 to 270° C. for 1 to 30 minutes.

In the case where the vulcanization is effected by irradiation withelectron beam without incorporating the vulcanizing agent (F), thepreliminarily formed rubber composition may be irradiated with anelectron beam of energy of 0.1 to 10 MeV, preferably 0.3 to 2 MeV so asto reach an absorbed dose of 0.5 to 35 Mrad, preferably 0.5 to 10 Mrad.For effecting the molding vulcanization, a mold may or may not be used.In the case wherein no mold is used, the rubber composition is usuallymolded and vulcanized in a continuous manner.

The rubber composition according to the present invention renders boththe improvement in the braking performance due to the improvement of thegripping ability on the road face and the improvement in the fuelconsumption performance due to reduction of rolling resistance duringsteady maneuvering, so that tires having both excellent brakingperformance and fuel consumption performance can be obtained by usingthe rubber composition according to the invention as the raw material.The rubber composition according to the invention is also excellent inweather resistance, ozone resistance, rubber elasticity, mechanicalstrength and the like.

The rubber composition according to the invention may be widely used asstarting materials of rubber articles, but it can be suitably used asthe rubber material for tires. Specific examples of the rubber materialfor tires include materials for tire tread and for tire side wall. Aboveall, the rubber composition according to the invention can be mostpreferably used for the material (raw material) for tire tread, wherebytires having both excellent braking performance and fuel consumptionperformance, and weather resistance, ozone resistance and the like canbe obtained, in which the characteristic properties of the rubbercomposition according to the invention are most effectively revealedtherefore.

The rubber composition according to the invention may comprise only thenonconjugated polyene copolymer (A) and the diene-based rubber (B) ormay comprise other rubber(s), other resin(s), a vulcanizing agent (F), avulcanization aid, a vulcanization accelerator, a filler (G) and othercomponents, for example, the above-mentioned additives.

The content of the nonconjugated polyene copolymer (A) and thediene-based rubber (B) in the rubber composition according to theinvention is in the range of preferably 3% by weight or more, morepreferably 5 to 90% by weight. The rubber composition according to theinvention has both excellent braking performance and fuel consumptionperformance, and has also excellent rubber elasticity, mechanicalstrength, weather resistance, ozone resistance, hardness and the like.

[Modifier for Tires]

The modifier for tires according to the invention comprises thenonconjugated polyene copolymer (A) according to the invention. Forexample, the modifier for tires according to the invention can be addedto the tires comprising the diene-based rubber, to thus provide tireshaving both excellent braking performance and fuel consumptionperformance, and also having excellent rubber elasticity, mechanicalstrength, weather resistance, ozone resistance, hardness and the like.

[Rubber Material for Tires]

The rubber material for tires according to the invention comprises therubber composition according to the invention. The rubber material fortires according to the invention has both excellent braking performanceand fuel consumption performance, and also has excellent rubberelasticity, mechanical strength, weather resistance, ozone resistance,hardness and the like.

[Tire Tread and Tire]

The tire tread according to the invention is produced by vulcanizing therubber material for tires according to the invention. The tire tread hasboth excellent braking performance and fuel consumption performance, andalso has excellent weather resistance, ozone resistance and the like.Further, the tire according to the invention are provided with the tiretread. The tire according to the invention has both excellent brakingperformance and fuel consumption performance, and also has excellentweather resistance, ozone resistance and the like.

EXAMPLES

Hereinafter, the present invention will be more specifically describedby way of Examples, but it is not intended to limit the presentinvention thereto.

Example X1

The polymerization was carried out in a continuous way using a reactorequipped with a stirrer made of a stainless steel (SUS) and having acapacity of 300 liters, while maintaining the temperature at 80° C. andkeeping the solution level at 100 L.(t-Butylamido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanetitaniumdichloride as a main catalyst, (C₆H₅)₃CB(C₆F₅)₄ as a co-catalyst andtriisobutylaluminum (hereinafter denoted as “TIBA”) as an organoaluminumcompound were used. Raw material supply conditions are as follows: TABLE1 Eth- Pro- Main Co- Hexane ylene pylene ENB Hydrogen catalyst catalystTIBA kg/h kg/h kg/h kg/h Nl/h mmol/h mmol/h mmol/h 24.5 3.7 3.8 4.5 200.27 0.81 2.5

The polymerization solution obtained was subjected to a standard steamstripping operation to obtain a resin. The copolymer obtained had anethylene content of 64.4 mol %, a propylene content of 30.1 mol %, anENB content of 5.5 mol % and a Mooney viscosity [ML(1+4)100° C.] of 55.The yield was 5.6 kg per hour.

Example X2

Polymerization was carried out under the same conditions as in ExampleX1 except that the material supply conditions were changed. The rawmaterial supply conditions are as follows: TABLE 2 Eth- Pro- Main Co-Hexane ylene pylene ENB Hydrogen catalyst catalyst TIBA kg/h kg/h kg/hkg/h Nl/h mmol/h mmol/h mmol/h 24.6 3.8 3.8 4.2 22 0.26 0.78 2.5

The copolymer obtained had an ethylene content of 65.1 mol %, apropylene content of 30.3 mol %, an ENB content of 4.6 mol % and aMooney viscosity [ML(1+4)100° C.] of 55. The yield was 5.6 kg per hour.

Comparative Example X1

Polymerization was carried out under the same conditions as in ExampleX1 except that the material supply conditions were changed. The rawmaterial supply conditions are as follows: TABLE 3 Eth- Pro- Main Co-Hexane ylene pylene ENB Hydrogen catalyst catalyst TIBA kg/h kg/h kg/hkg/h Nl/h mmol/h mmol/h mmol/h 22.8 3.7 3.8 6.2 20 0.28 0.84 2.5

The copolymer obtained had an ethylene content of 62.8 mol %, apropylene content of 29.8 mol %, an ENB content of 7.4 mol % and aMooney viscosity [ML(1+4)100° C.] of 55. The yield was 5.9 g per hour.

Comparative Example X2

Polymerization was carried out under the same conditions as in ExampleX1 except that the material supply conditions were changed. The rawmaterial supply conditions are as follows: TABLE 4 Eth- Pro- Main Co-Hexane ylene pylene ENB Hydrogen catalyst catalyst TIBA kg/h kg/h kg/hkg/h Nl/h mmol/h mmol/h mmol/h 24.9 3.9 3.8 3.7 23 0.25 0.75 2.5

The resin obtained had an ethylene content of 65.9 mol %, a propylenecontent of 30.6 mol %, an ENB content of 3.5 mol % and a Mooneyviscosity [ML(1+4)100° C.] of 55. The yield was 5.5 kg per hour.

Comparative Example X3

Polymerization was carried out under the same conditions as in ExampleX1 except that the catalyst and the material supply conditions werechanged, the polymerization temperature was 40° C. and thepolymerization solution was subjected to standard decalcification beforesteam stripping. Dichloroethoxyvanadium oxide was used as a maincatalyst and ethylaluminum sesquichloride was used as a co-catalyst. Theraw material supply conditions are as follows: TABLE 5 Main Co- HexaneEthylene Propylene ENB Hydrogen catalyst catalyst kg/h kg/h kg/h kg/hNl/h mmol/h mmol/h 44.6 1.2 10.6 1.11 7 9 63

The copolymer obtained had an ethylene content of 60.9 mol %, apropylene content of 30.1 mol %, an ENB content of 9.0 mol % and aMooney viscosity [ML(1+4)100° C.] of 55. The yield was 0.71 kg per hour.

The results are collectively shown in the following Table 6. TABLE 6Comp. Ex. Comp. Ex. Comp. Ex. X1 Ex. X2 X1 X2 Ex. X3 Ethylene 64.4 65.162.8 65.9 60.9 (mol %) Propylene 30.1 30.3 29.8 30.6 30.1 (mol %) ENB(mol %) 5.5 4.6 7.4 3.5 9.0 Iodine value 38 32 48 26 57 (g/100 g) ML(1 + 4) 100° C. 55 55 55 55 55 B value *1 1.06 1.06 1.06 1.06 1.35 Tg (°C.)*2 −17 −19 −5 −25 −5*1: B value was calculated as follows:First, the following nine NMR integration values were obtained: (1) αβ,(2) αγ + αδ, (3) βγ, (4) βδ, (5) γδ, (6) δδ, (7) 3E, (8) 3Z and (9) αα +1Z + 5E + 5Z + 6E + 6Z

Herein, a symbol consisting of numbers and alphabetic characters in (7)to (9) is carbons derived from ENB, and the numbers indicate thepositions in the formula given below, and the alphabetic characters, Eand Z denote E isomer and Z isomer, respectively. Further, Greekcharacters indicate the positions of carbon atoms located between carbonatoms on the main chain wherein two shortest methyl groups are bondedwith each other and a carbon atom adjacent to a carbon atom to which themethyl group is bonded, is assumed as α. For example, the carbon atom onthe main chain is adjacent to a carbon atom to which one methyl group isbonded and ay is assigned to a carbon atom at the third in distance fromthe carbon atom to which the other methyl group is bonded.

When the integration values were actually calculated, (2) was a total ofthe plural peaks near 37 to 39 ppm, (6) was a value obtained bysubtracting the γγ and γδ peaks from the total of the plural peaks near29 to 31 ppm, and (9) was the total of the plural peaks near 44 to 48ppm.

Further, αα was calculated as follows. The identification of the peakswas done according to the above literature:αα=αα+1Z+5E+5Z+6E+6Z−2×3E−3×3Z=(9)−2×(7)−3×(8)

Subsequently, the 6 dyads obtained from three monomers were calculatedfrom the obtained integration values as follows. Further, the dyads ofNN (ENB-ENB chain) and NP (ENB-propylene chain) derived from a smallcomposition of ENB was 0 and the dyad of NE had twice the valuecorresponding to a molar fraction calculated from absorption intensityassigned to a carbon atom on a cyclic ENB.

PP (propylene-propylene chain)=αα+αβ/4

PE (propylene-ethylene chain)=αγ+αδ+αβ/2

EE (ethylene-ethylene chain)=(βδ+δδ)/2+(γδ+βγ)/4

NE (ENB-ethylene chain)=(3E+3Z)×2

Finally, each molar fraction of the composition was determined asfollows:

a (ethylene molar fraction)=(EE+PE/2)/(PP+PE+EE+3E+3Z)

c (ethylene/α-olefin dyad molar fraction)=PE/(PP+PE+EE+NE)

d (ethylene/nonconjugated polyene dyad molar fraction)=NE/(PP+PE+EE+NE)

e (α-olefin molar fraction)=(PP+PE/2)/(PP+PE+EE+3E+3Z)

f (nonconjugated polyene molar fraction)=(3E+3Z)/(PP+PE+EE+3E+3Z)

Each molar fraction of the composition calculated above, is assigned tothe mathematical expression 1 to determine the mathematical expression2, and thus the B value was calculated:B=[(PE+NE)/(PP+PE+NE+EE)]/[(EE+PE/2)[(PP+PE/2)+(3E+3Z)]/(PP+PE+EE+3E+3Z)²]  [2]

In the mathematical expression 2, it shows that the larger the B value,the shorter the block chain of α-olefin (propylene) units ornonconjugated cyclic polyene units and the distribution of α-olefin(propylene) units and nonconjugated cyclic polyene units is uniform. Onthe contrary, it shows that the smaller the B value, the distribution ofthe nonconjugated cyclic polyene copolymer is not uniform and the longerthe block chain.

*2: Tg: the nonconjugated cyclic polyene copolymer was press molded at190° C. to form a strip sample of 10 mm width, 2 mm thickness and 30length. The dynamic viscoelasticity measurement was carried out by usingthis sample on a testing apparatus RDS-II (manufactured by RheometricsInc.) under conditions of a frequency of 10 Hz, a strain of 0.1% and atemperature elevation rate of 2° C./min, wherein the peak temperature onthe damping rate (tan δ) is assumed as Tg.

Example X3, and Comparative Examples X4, X5, X6 and X7

Using the components as given in the following Table 7 in a proportiongiven therein, a unvulcanized rubber blend was prepared by kneading themon an open roll (the front roll/the rear roll=60° C./60° C., 16/18 rpm).This rubber blend was processed on a press heated at 160° C. for 15minutes into a vulcanized sheet, with which the following tests werecarried out. The results are shown in the following Table 8. TABLE 7Comp. Ex. Comp. Ex. Comp. Ex. Comp. Ex. Ex. X3 X4 X5 X6 X7 Copolymer 30— — — — of Ex. X1 *1 Copolymer — 30 — — — of Comp. Ex. X1 *2 Copolymer —— 30 — — of Comp. Ex. X2 *3 Copolymer — — — 30 — of Comp. Ex. X3 *4 SBR*5 70 70 70 70 100 Zinc white 3 3 3 3 Stearic acid 1 1 1 1 1 HAF carbon50 50 50 50 50 black *6 Vulcanization 1.5 1.5 1.5 1.5 1.5 acceleratorCBZ *7 Sulfur 1.75 1.75 1.75 1.75 1.75*1: Copolymer of Example X1: see Table 1*2: Copolymer of Comparative Example X1: see Table 3*3: Copolymer of Comparative Example X2: see Table 4*4: Copolymer of Comparative Example X3: see Table 5*5: SBR: a styrene/butadiene rubber, NIPOL 1502 (trademark), a productof ZEON Corporation, iodine value = 357*6: HAF carbon black: = HAF ASAHI #70 (trademark), a product of AsahiCarbon Co., Ltd.*7: Vulcanization accelerator CBZ: SANCELER CM (trademark), a product ofSanshin Chemical Industry Co., Ltd.

TABLE 8 Comp. Ex. Comp. Ex. Comp. Ex. Comp. Ex. Ex. X3 X4 X5 X6 X7 M₁₀₀4.00 4.21 3.89 4.74 2.90 (MPa) *1 T_(B) (MPa) *2 21.6 21.8 19.8 20.824.2 E_(B) (%) *3 270 280 250 270 400 H_(A) (SHORE 71 71 70 74 67 A) *4tan δ 0.29 0.37 0.22 0.33 0.16 (0° C.) *5 tan δ 0.14 0.13 0.14 0.13 0.15(60° C.) *5 Resistance 16440 14490 16480 12350 18450 fatigue (dam- aged)*6 Resistance 39450 32470 39940 28450 70440 fatigue (no damaged) *7*1: M₁₀₀: Tensile stress at 100% elongation was measured according toJIS K6251. The smaller the M100, the lower the hardness and the broaderthe ground contact area, and thus braking performance of a tire is good.*2: T_(B): Tensile strength at break was measured according to JISK6251.*3: E_(B): Tensile elongation was measured according to JIS K6251.*4: H_(A) (Shore A) = Shore A hardness was measured according to JISK6253.*5: tan δ: The tan δ (damping rate) of the rubber composition(crosslinked in a proportion of Table 6) at 0° C. was represented as anindex of braking performance of a tire. The larger is the tan δ at 0°C., the more excellent the braking performance of the tire is. The tan δ(damping rate) of the rubber composition at 60° C. was represented as anindex of fuel consumption of a vehicle. The smaller the tan δ at 60° C.,# the more excellent the fuel consumption of the vehicle is. The tan δ(damping rate) is determined, using a strip sample of 10 mm width, 2 mmthickness and 30 mm length prepared from the rubber composition, on atesting apparatus RDS-II (manufactured by Rheometrics Inc.) from thetemperature dispersion of viscoelasticity observed under conditions of0.05% strain and 10 Hz frequency.*6: Fatigue resistance (damaged): Dumbbell-shaped No. 1 test piecesdescribed in JIS K 6251 were punched from the vulcanized rubber sheetand the test pieces had dents of 2 mm formed at the center of thelongitudinal direction. The five test pieces thus obtained weresubjected to extension fatigue under conditions of an extension rate of40%, a preset temperature of 23° C. and a rotation speed of 300times/min using a constant elongation, constant load fatigue tester(Model FT-3121,# manufactured by Ueshima Seisakusho Co., Ltd.). An average value of thetimes at which the dumbbells were broken was determined.*7: Fatigue resistance (no damaged): Dumbbell-shaped No. 1 test piecesdescribed in JIS K 6251 were punched from the vulcanized rubber sheet.The five test pieces were subjected to extension fatigue underconditions of an extension rate of 100%, a preset temperature of 23° C.and a rotation speed of 300 times/min using a constant elongation,constant load fatigue tester (Model FT-3121,# manufactured by Ueshima Seisakusho Co., Ltd.). An average value of thetimes at which the dumbbells were broken was determined.

Example Y1

The polymerization was carried out in a continuous way using a reactorequipped with a stirrer made of a stainless steel (SUS) and having acapacity of 300 liters, while maintaining the temperature at 40° C. andkeeping the solution level at 100 L. The polymerization solution afterpolymerization was subjected to standard decalcification and thensubjected to steam stripping to obtain a polymer. Dichloroethoxyvanadiumoxide was used as a main catalyst and ethylaluminum sesquichloride wasused as a co-catalyst. The raw material supply conditions are asfollows: TABLE 9 Main Co- Hexane Ethylene Propylene ENB Hydrogencatalyst catalyst kg/h kg/h kg/h kg/h Nl/h mmol/h mmol/h 41.0 3.3 12.12.44 35 75 525

The copolymer obtained had an ethylene content of 61.1 mol %, apropylene content of 29.9 mol %, an ENB content of 9.0 mol % and aMooney viscosity [ML(1+4)100° C.] of 55. The yield was 5.70 kg per hour.

Example Y2

Polymerization was carried out under the same conditions as in ExampleY1 except that the material supply conditions were changed. The rawmaterial supply conditions are as follows: TABLE 10 Eth- Pro- Main Co-Hexane ylene pylene ENB VNB Hydrogen catalyst catalyst kg/h kg/h kg/hkg/h Kg/h Nl/h mmol/h mmol/h 41.5 5.3 12.1 1.73 0.26 38 75 525

The polymerization solution obtained was subjected to a standarddecalcification and then subjected to steam stripping to obtain a resin.The resin obtained had an ethylene content of 62.8 mol %, a propylenecontent of 29.8 mol %, an ENB content of 6.40 mol %, a VNB content of0.98 mol % and a Mooney viscosity [ML(1+4)100° C.] of 55. The yield was5.9 kg per hour. The insoluble content was 38%.

Comparative Example Y1

Polymerization was carried out under the same conditions as in ExampleY1 except that the material supply conditions were changed. The rawmaterial supply conditions are as follows: TABLE 11 Main Co- HexaneEthylene Propylene ENB Hydrogen catalyst catalyst kg/h kg/h kg/h kg/hNl/h mmol/h mmol/h 44.6 1.2 10.6 1.11 7 9 63

The copolymer obtained had an ethylene content of 60.9 mol %, apropylene content of 30.1 mol %, an ENB content of 9.0 mol % and aMooney viscosity [ML(1+4)100° C.] of 55. The yield was 0.71 kg per hour.

The results are collectively shown in the following Table 12. TABLE 12Comparative Example Y1 Example Y2 Example Y1 Ethylene (mol %) 61.1 62.860.9 Propylene (mol %) 29.9 29.8 30.1 ENB (mol %) 9.0 6.4 9.0 VNB (mol%) — 0.98 — Iodine value (g/100 g) 56 48 57 ML(1 + 4) 100° C. 55 55 55Tg (° C.) *1 −5 −11 −5 Decalin insoluble content 0.8 38 Less than 0.2 at135° C.*1: Measured in the same manner as in a footnote *2 in Table 6*2: 0.25 g (±10%) of a sample finely cut was weighed (A(g)) andintroduced into a 500-ml Erlenmeyer flask, and then 250 ml of decalin isadded thereto. A rotator was placed in the Erlenmeyer flask and theflask was capped. The flask was put in an aluminum block bath havingliquid temperature of 135° C. to preheat for 15 minutes. Thereafter, therotator was rotated to carry out dissolution under stirring for 60minutes. The dissolved sample is filtered using a 150-mesh stainless# wire gauze vessel previously weighed (B(g)). The inside of the flaskwas washed with fresh decalin (room temperature) and filtered, whereinthis operation was repeated three times. Further, the inside of the wiregauze vessel was washed with fresh decalin (room temperature). The wiregauze vessel was dried for 1 hour using a vacuum drier at 105 ± 5° C.After standing to cool to room temperature, the weight of the wire gauzevessel was weighed (C(g)). The decalin insoluble # content is calculatedfrom three weights obtained above by the following formula: Decalininsoluble content (%) = (C − B) × 100/A

Examples Y3 and Y4, and Comparative Example Y2

Using the components as given in the following Table 13 in a proportiongiven therein, a unvulcanized rubber blend was prepared by kneading themon an open roll (the front roll/the rear roll=60° C./60° C., 16/18 rpm).This rubber blend was processed on a press heated at 160° C. for 15minutes into a vulcanized sheet, with which the following tests werecarried out. The results are shown in the following Table 14. TABLE 13Example Example Comparative Y3 Y4 Example Y2 Copolymer of Ex. Y1 *1 30 —— Copolymer of Ex. Y2 *2 — 30 — Copolymer of Comp. Ex. Y1 *3 — — 30 SBR*4 70 70 70 Zinc white 3 3 3 Stearic acid 1 1 1 HAF carbon black *5 5050 50 Vulcanization accelerator CBZ *6 1.5 1.5 1.5 Sulfur 1.75 1.75 1.75*1: Copolymer of Example Y1: see Table 9*2: Copolymer of Example Y2: see Table 10*3: Copolymer of Comparative Example Y1: see Table 11*4: the same as a footnote *5 in Table 7*5: HAF carbon black: the same as a footnote *6 in Table 7*6: Vulcanization accelerator CBZ: the same as a footnote *7 in Table 7

TABLE 14 Example Example Comparative Y3 Y4 Example Y2 T_(B) (MPa) *123.5 25.1 20.8 E_(B) (%) *2 310 350 270 H_(A) (SHORE A) *3 74 74 74 tanδ (0° C.) *4 0.33 0.33 0.33 tan δ (60° C.) *4 0.13 0.13 0.13*1: T_(B): Elongation at break, measured in the same manner as in afootnote *2 in Table 8*2: E_(B): Tensile elongation, measured in the same manner as in afootnote *3 in Table 8*3: H_(A) (Shore A) = Shore A hardness, measured in the same manner asin a footnote *4 in Table 8*4: tan δ: Measured in the same manner as in a footnote *5 in Table 8using the rubber composition crosslinked in a proportion of Table 13

Example Z1

The polymerization was carried out in a continuous way using a reactorequipped with a stirrer made of a stainless steel (SUS) and having acapacity of 300 liters, while maintaining the temperature at 80° C. andkeeping the solution level at 100 L.(t-Butylamido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanetitaniumdichloride as a main catalyst, (C₆H₅)₃CB(C₆F₅)₄ as a co-catalyst andtriisobutylaluminum as an organoaluminum compound were used. Rawmaterial supply conditions are as follows: TABLE 15 Main Co- HexaneEthylene Propylene ENB VNB Hydrogen catalyst catalyst TIBA kg/h kg/hkg/h kg/h Kg/h Nl/h mmol/h mmol/h mmol/h 22.8 3.7 3.8 6.0 0.25 23 0.280.84 2.5

The polymerization solution obtained was subjected to a standard steamstripping operation to obtain a resin. The resin obtained had anethylene content of 62.8 mol %, a propylene content of 29.8 mol %, anENB content of 7.14 mol %, a VNB content of 0.26 mol % and a Mooneyviscosity [ML(1+4)100° C.] of 55. The yield was 5.9 kg per hour.

Comparative Example Z1

Polymerization was carried out under the same conditions as in ExampleZ1 except that the material supply conditions were changed. The rawmaterial supply conditions are as follows: TABLE 16 Main Co- HexaneEthylene Propylene ENB VNB Hydrogen catalyst catalyst TIBA kg/h kg/hkg/h kg/h Kg/h Nl/h mmol/h mmol/h mmol/h 22.8 3.7 3.8 6.0 — 20 0.28 0.842.5

The resin obtained had an ethylene content of 62.8 mol %, a propylenecontent of 29.8 mol %, an ENB content of 7.4 mol % and a Mooneyviscosity [ML(1+4)100° C.] of 55. The yield was 5.9 kg per hour.

Comparative Example Z2

Polymerization was carried out under the same conditions as in ExampleZ1 except that the material supply conditions were as given in thefollowing Table. TABLE 17 Main Co- Hexane Ethylene Propylene ENB VNBHydrogen catalyst catalyst TIBA kg/h kg/h kg/h kg/h Kg/h Nl/h mmol/hmmol/h mmol/h 27.9 2.9 5.5 5.8 — 20 0.28 0.84 2.5

The resin obtained had an ethylene content of 49.6 mol %, a propylenecontent of 43.4 mol %, an ENB content of 7.0 mol % and a Mooneyviscosity [ML(1+4)100° C.] of 52. The yield was 5.0 kg per hour.

The results are collectively shown in the following Table 18. TABLE 18Comparative Comparative Example Z1 Example Z1 Example Z2 Ethylene (mol%) 62.8 62.8 49.6 Propylene (mol %) 29.8 29.8 43.4 ENB (mol %) 7.14 7.47.0 VNB (mol %) 0.26 — — Iodine value (g/100 g) 48 48 64 ML(1 + 4)100°C. 55 55 52 B value *1 1.06 1.06 1.05 Tg (° C.) *2 −5 −5 −18 η_(0.1)* *332100 20390 19520 η₁₀* *3 3710 3660 3740 η_(0.1)*/η₁₀* 0.0148 0.01260.0121*1: B value: Measured in the same manner as in a footnote *1 in Table 6*2: Tg: Measured in the same manner as in a footnote *2 in Table 6*3: η_(0.1)* and η₁₀*: The frequency dependency of η* (complex viscositycoefficient) is determined, using a disk-shaped sample having a diameterof 25 mm and a thickness of 2 mm, on a viscoelasticity tester (Model RDSII, manufactured by Rheometrics Inc.) under conditions of a measuringtemperature of 190° C., a frequency of 0.01 to 500 rad/s and a strainratio of 1.0%. η_(0.1)* indicates complex viscosity coefficient at thefrequency of 0.1 rad/s# and η₁₀* indicates complex viscosity coefficient at the frequency of10 rad/s.

Example Z2, and Comparative Examples Z3 and Z4

Using the components as given in the following Table 19 in a proportiongiven therein, a unvulcanized rubber blend was prepared by kneading themon an open roll (the front roll/the rear roll=60° C./60° C., 16/18 rpm).This rubber blend was processed on a press heated at 160° C. for 15minutes into a vulcanized sheet, with which the following tests werecarried out. The results are shown in the following Table 20. TABLE 19Example Comparative Comparative Z2 Example Z3 Example Z4 Copolymer ofEx. Z1 *1 30 — — Copolymer of Comp. Ex. — 30 — Z1 *2 Copolymer of Comp.Ex. — — 30 Z2 *3 SBR*4 70 70 70 Zinc white 3 3 3 Stearic acid 1 1 1 HAFcarbon black *5 50 50 50 Vulcanization accelerator 1.5 1.5 1.5 CBZ *6Sulfur 1.75 1.75 1.75*1: Copolymer of Example Z1: see Table 15*2: Copolymer of Comparative Example Z1: see Table 16*3: Copolymer of Example Z2: see Table 17*4: the same as a footnote *5 in Table 7*5: HAF carbon black: the same as a footnote *6 in Table 7*6: Vulcanization accelerator CBZ: the same as a footnote *7 in Table 7

TABLE 20 Comparative Comparative Example Z2 Example Z3 Example Z4 T_(B)(MPa) *1 23.5 21.8 19.5 E_(B) (%) *2 330 280 250 H_(A) (SHORE A) *3 7171 69 tan δ (0° C.) *4 0.37 0.37 0.37 tan δ (60° C.) *4 0.13 0.13 0.13*1: T_(B): Elongation at break, measured in the same manner as in afootnote *2 in Table 8*2: E_(B): Tensile elongation, measured in the same manner as in afootnote *3 in Table 8*3: H_(A) (Shore A) = Shore A hardness, measured in the same manner asin a footnote *4 in Table 8*4: tan δ: measured in the same manner as in a footnote *5 in Table 8using the rubber composition crosslinked in a proportion of Table 19

1. A nonconjugated polyene copolymer comprising a random copolymerhaving structural units derived from α-olefin (A1) of 2 to 20 carbonatoms and structural units derived from nonconjugated polyene (A2), saidnonconjugated polyene copolymer having a glass transition temperature(Tg) of −25 to 20□ and Mooney viscosity of [ML(1+4)100□] of 5 to
 190. 2.The nonconjugated polyene copolymer according to claim 1, saidnonconjugated polyene copolymer comprising a random copolymer havingstructural units derived from α-olefin (A1) of 2 to 20 carbon atoms andstructural units derived from nonconjugated cyclic polyene (A3), whereinthe content of structural units derived from α-olefin (A1) of 2 to 20carbon atoms is more than 93 to 96 mol % and the content of structuralunits derived from nonconjugated cyclic polyene (A3) is 4 to less than 7mol %.
 3. The nonconjugated polyene copolymer according to claim 2,wherein the nonconjugated polyene copolymer (A) consists only of thestructural units derived from (A1) and the structural units derived from(A3).
 4. The nonconjugated polyene copolymer according to claim 2,wherein the structural units derived from α-olefin (A1) of 2 to 20carbon atoms contain at least structural units derived from ethylene andthe molar ratio of the structural units derived from ethylene/structuralunits derived from α-olefin of 3 or more carbon atoms is in the range of100/0 to 1/99.
 5. The nonconjugated polyene copolymer according to claim2, wherein the content of structural units derived from ethylene of thenonconjugated polyene copolymer is in the range of 50 mol % or morebased on 100 mol % of the total amount of α-olefin (A1) having 2 to 20carbon atoms and nonconjugated cyclic polyene (A3) and a B valueindicated below satisfies the relationship of the following formula [1]:B≦(1/a−1)×0.4+1  [1] wherein B=(c+d)/(2×a×(e+f)), in which a is anethylene molar fraction; c is an ethylene/α-olefin dyad molar fraction;d is an ethylene/nonconjugated polyene dyad molar fraction; e is anα-olefin molar fraction; and f is a nonconjugated polyene molarfraction.
 6. The nonconjugated polyene copolymer according to claim 1,said nonconjugated polyene copolymer comprising a random copolymerhaving structural units derived from α-olefin (A1) of 2 to 20 carbonatoms and structural units derived from nonconjugated polyene (A2),wherein the content of structural units derived from α-olefin (A1) of 2to 20 carbon atoms is 70 to 96 mol % and the content of the structuralunits derived from nonconjugated polyene (A2) is 4 to 30 mol % and adecalin insoluble content at 135□ is 0.5% by weight or more.
 7. Thenonconjugated polyene copolymer according to claim 6, wherein thestructural units derived from α-olefin (A1) of 2 to 20 carbon atomscontain at least structural units derived from ethylene and the molarratio of the structural units derived from ethylene/structural unitsderived from α-olefin of 3 or more carbon atoms is in the range of 100/0to 1/99.
 8. The nonconjugated polyene copolymer according to claim 6,wherein at least part of the nonconjugated polyene (A2) of thenonconjugated polyene copolymer is the nonconjugated cyclic polyene(A3).
 9. The nonconjugated polyene copolymer according to claim 1,wherein the nonconjugated polyene copolymer is a random copolymer fromα-olefin (A1) of 2 to 20 carbon atoms and nonconjugated polyene (A2) andis a nonconjugated polyene copolymer which satisfies the following (iii)to (v) requirements: (iii) an iodine value is 30 g/100 g or more; (iv)it meets 0.0136≦(η_(0.1)*)^(0.3859)/η₁₀* wherein η_(0.1)* is a viscosityat 0.1 rad/sec (Pa·s) and η₁₀* is a viscosity at 10 rad/sec (Pa·s); and(v) the content of the structural units derived from ethylene is in therange of 50 mol % or more based on 100 mol % of the total amount ofα-olefin (A1) of 2 to 20 carbon atoms and nonconjugated polyene (A2) anda B value indicated below satisfies the relationship of the followingformula [1]:B≦(1/a−1)×0.4+1  [1] wherein B=(c+d)/(2×a×(e+f)), in which a is anethylene molar fraction; c is an ethylene/α-olefin dyad molar fraction;d is an ethylene/nonconjugated polyene dyad molar fraction; e is anα-olefin molar fraction; and f is a nonconjugated polyene molarfraction.
 10. The nonconjugated polyene copolymer according to claim 9,wherein the nonconjugated polyene copolymer contains the content ofstructural units derived from α-olefin (A1) of 2 to 20 carbon atomsbeing 70 to 96 mol % and the content of structural units derived fromnonconjugated polyene (A2) being 4 to 30 mol %.
 11. The nonconjugatedpolyene copolymer according to claim 9, wherein at least part of thenonconjugated polyene (A2) of the nonconjugated polyene copolymer is thenonconjugated cyclic polyene (A3).
 12. A rubber composition comprisingthe nonconjugated polyene copolymer according to claim 1 and adiene-based rubber (B).
 13. The rubber composition according to claim12, wherein the nonconjugated polyene copolymer is the nonconjugatedpolyene copolymer according to any one of claims 2 to 11 and the weightratio of the nonconjugated polyene copolymer/diene rubber (B) is in therange of 60/40 to 0.1/99.9.
 14. A modifier for tires comprising thecopolymer according to claim
 1. 15. A rubber material for tirescomprising the rubber composition according to claim
 12. 16. A rubbermaterial for tires comprising the rubber composition according to claim13.
 17. A tire tread obtained from the rubber material for tiresaccording to claim
 12. 18. A tire having the tire tread according toclaim 17.